Legally? Not really.
I suppose you could try one of the many download accelerator softwares that there are. I personally found them not much use though.
If your speeds are crap constantly, then I’d start looking for a new provider.
Please go to www.speedtest.net, run their test, and post the output here so we can see what your speeds are - when the test has run, there will be a link in [IMG] tags for you to copy’n’paste, and post to the forum.
Edit: Here is mine as an example: